It is known to provide a probe for measuring characteristics of a hardenable construction material. For example, one known system for measuring the hardness of concrete (see U.S. Pat. No. 6,023,170) uses at least two electrodes which are placed in the concrete for the purpose of measuring the dielectric characteristics of the concrete, which are related to the hardness of the concrete.
It is known to provide a probe structure as shown in FIG. 1. The probe 2 comprises a base 4 and two hollow cylindrical metal tubes 6, and is supported in wooden formwork 8. The probe 4 is first attached to a holder 10 by sliding the cylindrical metal tubes 6 on to two prongs 12 of the holder 10. The probe 2 is then supported on the inside of the formwork 8 by disposing a central cylindrical section 14 of the holder within a hole drilled in the formwork 8. Flanges 16 of the holder 10 have holes extending therethrough to permit the holder 10 to be fastened to the formwork using screws 18. After the concrete has set, the holder 10 can be removed, thus permitting the terminals of a connector to be fitted into the cylindrical metal tubes 6, thereby enabling a measurement of dielectric characteristics of the concrete surrounding the tubes 6.
This arrangement suffers from a number of disadvantages. First, the dielectric measurements made using the probe 2 do not distinguish clearly between materials of different characteristics, particularly when the characteristics are similar. Second, the holder 10 can only be removed to permit connection of an instrument after the material within which the probe 2 is embedded has hardened. Accordingly, the probe cannot be used during the initial stages of hardening. A further disadvantage is that the construction of the holder 10 is such that it can only be used with wooden formwork or shuttering 8 in which the screws 18 can be fastened, and only with shuttering 8 of a limited range of thicknesses. Also, there is a significant chance of leakage of the hardening material through the hole drilled in the formwork 8, around the circumference of the holder 10.
It would be desirable to provide an arrangement which overcomes or mitigates at least some of these disadvantages. It would also be desirable to provide a measurement system which can be used throughout a very wide range of situations.
It would be desirable to provide a measurement probe which can be used for hardness testing within an experimental set-up, as well for “in-situ” strength measurements of concrete in a variety of different physical locations, which vary in their accessibility as well as in the size and shape of the concrete masses. It would also be desirable to achieve this while using a low-cost, consumable, embedded measurement probe.